In various multistage turbomachines used for energy conversion, such as gas turbines, a fluid is used to produce rotational motion. Referring to FIG. 1, an axial flow gas turbine 10 includes a compressor section 12, a combustion section 14 and a turbine section 16 arranged along a horizontal center axis 17. The compressor section 14 provides a compressed air flow to the combustion section 14 where the air is mixed with a fuel, such as natural gas, and ignited to create a hot working gas. The turbine section 16 includes a plurality of blade assemblies 20 arranged in a plurality of rows. The hot gas expands through the turbine section 16 where it is directed across the rows of blade assemblies 20 by associated stationary vanes 22. The blade assemblies 20 are ultimately attached to a shaft that is rotatable about the center axis 17. As the hot gas passes through the turbine section 16, it causes the blade assemblies 20 and thus the shaft to rotate, thereby providing mechanical work. Each row of blade assemblies 20 and associated vanes 22 form a stage. In particular, the turbine section 16 may include four rows of blade assemblies 20 and associated vanes 22 to form four stages. The gas turbine 10 further includes an exhaust cylinder section 18 located adjacent the turbine section 16 and an outer diffuser section 24 located adjacent the exhaust cylinder section 18.
Many gas turbines may utilize a portion of the compressed air generated by the compressor section 12 as a cooling fluid for cooling hot components of the combustion 14 and turbine sections 16 of the gas turbine 10. In one type of cooling system design known as a closed loop cooling system, a seal pin arrangement is used to form a seal between adjacent rotating blade assemblies 20. FIG. 2 illustrates an exemplary rotatable blade assembly 20 used in the gas turbine 10. Blade assembly 20 includes a root section 26 that is attached to a rotor and a platform section 28 that extends from the root section 26. An airfoil or turbine blade 30 extends from the platform 28 on an opposite side from the root section 26. The platforms 28 are located on the rotor such that each blade 30 is substantially evenly spaced from an adjacent blade 30. The blade 30 extracts heat and pressure energy from the hot gas as it passes over the blade assembly 20 and converts the energy into mechanical energy by rotating the shaft.
The platform 28 is sealed and damped against a corresponding platform 28 of an adjoining blade assembly 20 by seal pins 32 and 34. The pins 32 and 34 are positioned in corresponding pin slots 36 and 38 formed into a surface 40 of the platform 28. The pin slots 36 and 38 are arranged such that centrifugal force generated by rotation about the center axis 17 loads the pins 32 and 34. This forces the pins 32 and 34 out of a resting position in the pin slots 36 and 38 so that the pins 32 and 34 are urged against a corresponding surface of a platform 28 of an adjoining blade assembly 20, thereby forming a seal and damping structure.